[gradle] Accessing files in build directory

[provide a description of the issue]

Environment

• Operating System: macOS Sierra
• JDK version: JDK 8
• Visual Studio Code version: 1.15
• Java extension version: 0.8.0

Steps To Reproduce

I track a build number using a text file in the build project directory, e.g., 'build.num'

First, the file can't be found using this code:

def buildNumber = new File("build.num").text.toInteger() + 1

It looks like gradle isn't being run in the same directory as the build.gradle file. So I changed the code to this:

def buildNumber = new File("${projectDir}/build.num").text.toInteger() + 1

Now the 'build.num' file is being found. The same problem exists when referencing any files from a relative location.

Current Result

File Not Found

Expected Result

Build should work the same as if running it from the build directory.

Additional Informations

Start by reproducing the Gradle build with the relative build.num path and compare it with the ${projectDir}/build.num form. Inspect how the VS Code Java extension launches Gradle and verify that the fix makes relative paths resolve from the build directory without breaking other builds.